This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We have crystals of an E. coli intramembrane protease in its full-length form. The structure of the membrane domain has been previously solved. Elucidation of the full length form along with the cytoplasmic domain may give clues to its function in E. coli which is currently unknown. Prokaryotic intramembrane proteases have been shown to play a role in quorum sensing. The eukaryotic forms of this protease are linked to disease states such as Type 2 diabetes, breast cancer and Parkinson's disease.